Method for making pine shaped metal nano-scaled grating

ABSTRACT

A method of making a pine shaped metal nano-scaled grating, the method including: forming a first metal layer on a substrate, forming an isolation layer on the first metal layer, and locating a second metal layer on the isolation layer; placing a first mask layer on the second metal layer, wherein the first mask layer comprises a body, and the body defines a plurality of openings parallel with and spaced apart from each other; etching the first mask layer and the second metal layer to obtain a plurality of triangular prism structures; etching the isolation layer to obtain a plurality of second rectangular structures using the plurality of triangular prism structures as a first mask; and etching the first metal layer to obtain a plurality of first rectangular structures using the plurality of second rectangular structures as a second mask.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. § 119 from China Patent Application No. 201710289458.7, filed on Apr. 27, 2017, in the China Intellectual Property Office, the disclosure of which is incorporated herein by reference.

FIELD

The subject matter herein generally relates to a method for making a pine shaped metal nano-scaled grating.

BACKGROUND

Metal nanostructures play an important role in many fields, such as nano-optics, biochemical sensor, precision optical instruments with ultra-high resolution imaging, surface plasma, and surface plasma lithography. In the prior art, metal nanostructures can be made by lift-off process, milling process of focused ion beam, or electrochemistry method. However, since the above methods can introduce chemical reagents, it is difficult to achieve a nanostructure having a specific morphology. So it is a challenges to make a metal nanostructure having a specific morphology.

In the processing of nanostructures, the rate of chemical corrosion depends on the chemical properties of materials. For example, since different crystal orientations of silicon have different corrosion rates, a specific silicon three-dimensional nanostructure can be obtained. However, it is difficult to obtain specific three-dimensional nanostructures for most metal crystals by chemical corrosion. Dry etching methods include reaction ion etching (RIE) method and inductively coupled plasma etching method. The rate of dry etching depends on the reaction surface of ions. The etching rate of the reaction surface is greater than the etching rate of the other surfaces. A specific nanostructure can be obtained by reasonable etching rate ratios. The focused ion beam induced etching (FIBIE) method is also one of the dry etching methods for preparing three-dimensional nanostructures. However, only inclined trough structures can be obtained by the FIBIE method, and the sizes of the inclined trough structures are too large and it is difficult to obtain etching masks. Furthermore, it is particularly difficult to obtain three-dimensional gold nanostructures.

What is needed, therefore, is to provide a method for making a pine shaped metal nano-scaled grating for solving the problem discussed above.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with references to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. Implementations of the present technology will now be described, by way of example only, with reference to the attached figures, wherein:

FIG. 1 is a structural schematic view of one embodiment of a pine shaped metal nano-scaled grating.

FIG. 2 is a sectional view of the pine shaped metal nano-scaled grating of FIG. 1.

FIG. 3 is a structural schematic view of one embodiment of a pine shaped metal nano-scaled grating forming different patterns.

FIG. 4 is an exploded view of one embodiment of the three-dimensional nanostructures.

FIG. 5 is a flow chart of one embodiment of a method for making the pine shaped metal nano-scaled grating.

FIG. 6 is a flow chart of one embodiment of a method for making a patterned first mask layer.

FIG. 7 is a low magnification Scanning Electron Microscope (SEM) image of the pine shaped metal nano-scaled grating.

FIG. 8 is a high magnification SEM image of the pine shaped metal nano-scaled grating.

FIG. 9 is a flow chart of one embodiment of a method for making the pine shaped metal nano-scaled grating.

FIG. 10 is a structural schematic view of one embodiment of a pine shaped metal nano-scaled grating.

FIG. 11 is a structural schematic view of one embodiment of a pine shaped metal nano-scaled grating.

FIG. 12 is a flow chart of one embodiment of a method for making the pine shaped metal nano-scaled grating.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. The drawings are not necessarily to scale, and the proportions of certain parts may be exaggerated to better illustrate details and features. The description is not to be considered as limiting the scope of the embodiments described herein.

Several definitions that apply throughout this invention will now be presented.

The connection can be such that the objects are permanently connected or releasably connected. The term “substantially” is defined to be essentially conforming to the particular dimension, shape or other word that substantially modifies, such that the component need not be exact. The term “comprising” means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in a so-described combination, group, series and the like. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one.

Referring to FIG. 1 and FIG. 2, an embodiment of a pine shaped metal nano-scaled grating 10 comprises a substrate 100 and a plurality of three-dimensional nanostructures 110 located on a surface of the substrate 100. The plurality of three-dimensional nanostructures 110 are pine shaped structures.

The substrate 100 can be an insulating substrate or a semiconductor substrate. The material of the substrate 100 can be silicon, silicon dioxide, silicon nitride, quartz, glass, gallium nitride, gallium arsenide, sapphire, alumina, or magnesia. The size, thickness and shape of the substrate 100 can be selected according to need. In one embodiment, the material of the substrate 100 is quartz.

The plurality of three-dimensional nanostructures 110 can be arranged side by side and extend along a straight line, a fold line, or a curve line. The extending direction is parallel to a first surface 1002 of the substrate 100. Referring to FIG. 3, the extending direction can be any direction which is parallel to the first surface 1002 of the substrate 100. The term “side by side” means that two adjacent three-dimensional nanostructures 110 are substantially parallel with each other along the extending direction. The distance between two adjacent three-dimensional nanostructures 110 is in a range from 0 nanometer to 200 nanometers. The plurality of three-dimensional nanostructures 110 can be continuous or discontinuous along the extending direction. In one exemplary embodiment, the plurality of three-dimensional nanostructures 110 are continuous, the extending direction of the three-dimensional nanostructures 110 extends side by side, the three-dimensional nanostructures are strip-shaped structures, and cross sections of the three-dimensional nanostructures have the same pine shapes and the same area.

Referring to FIG. 4, the three-dimensional nanostructures 110 are pine shaped ridges located on the first surface 1002 of the substrate 100. The pine shaped ridges comprise a first rectangular structure 121, a second rectangular structure 131, and a triangular prism structure 141. The first rectangular structure 121 comprises a first top surface 1212, and the first top surface 1212 is away from the substrate 100. The second rectangular structure 131 is located on the first top surface 1212. The second rectangular structure 131 comprises a second top surface 1312, and the second top surface 1312 is away from the first rectangular structure 121. The triangular prism structure 141 is located on the second top surface 1312. The geometric centers of the first rectangular structure 121, the second rectangular structure 131 and the triangular prism structure 141 are on the same axis. The first rectangular structure 121 and the triangular prism structure 141 are both metal layers. The second rectangular structure 131 can isolate the first rectangular structure 121 and the triangular prism structure 141.

The triangular prism structure 141 comprises a first triangle surface 1410 and a second triangle surface 1412 opposite to and substantially parallel with the first triangle surface 1410. The sizes and shapes of the first triangle surface 1410 and the second triangle surface 1412 are both the same. The triangular prism structure 141 further comprises a first rectangular side 1414, a second rectangular side 1416, and a third rectangular side 1418 connected to the first triangle surface 1410 and the second triangle surface 1412. The projection of the first triangle surface 1410 coincides with the projection of the second triangle surface 1412. The shapes of the first triangle surface 1410 and the second triangle surface 1412 are both isosceles triangle. The third rectangular side 1418 is in contact with the second top surface 1312 of the second rectangular structure 131. The side surface of the first rectangular structure 121 is perpendicular to the first surface 1002 of the substrate 100. The side surface of the second rectangular structure 131 is perpendicular to the first top surface 1212 of the first rectangular structure 121, thus the side surface of the second rectangular structure 131 is also perpendicular to the first surface 1002 of the substrate 100.

The width d1 of the first rectangular structure 121 is in a range of 5 nanometers to 400 nanometers, the height h1 of the first rectangular structure 121 is in a range of 20 nanometers to 500 nanometers. Furthermore, the width d1 of the first rectangular structure 121 can be in a range of 12 nanometers to 320 nanometers, the height h1 of the first rectangular structure 121 can be in a range of 50 nanometers to 200 nanometers. In one exemplary embodiment, the width d1 of the first rectangular structure 121 is 50 nanometers, the height h1 of the first rectangular structure 121 is 100 nanometers. The width d2 of the second rectangular structure 131 is in a range of 50 nanometers to 450 nanometers, the height h2 of the second rectangular structure 131 is in a range of 5 nanometers to 100 nanometers. Furthermore, the width d2 of the second rectangular structure 131 can be in a range of 80 nanometers to 380 nanometers, the height h2 of the second rectangular structure 131 can be in a range of 5 nanometers to 60 nanometers. In one exemplary embodiment, the width d2 of the second rectangular structure 131 is 100 nanometers, the height h2 of the second rectangular structure 131 is 10 nanometers. The width d3 of the triangular prism structure 141 is in a range of 50 nanometers to 450 nanometers, the height h3 of the triangular prism structure 141 is in a range of 40 nanometers to 800 nanometers. Furthermore, the width d3 of the triangular prism structure 141 can be in a range of 80 nanometers to 380 nanometers, the height h3 of the triangular prism structure 141 can be in a range of 130 nanometers to 400 nanometers. In one exemplary embodiment, the width d3 of the triangular prism structure 141 is 100 nanometers, the height h3 of the triangular prism structure 141 is 200 nanometers. The width d3 of the triangular prism structure 141 is the width of the third rectangular side 1418 of the triangular prism structure 141. The width d3 of the triangular prism structure 141 is equal to the width d2 of the second rectangular structure 131. The third rectangular side 1418 of the triangular prism structure 141 is completely coincident with the second top surface 1312 of the second rectangular structure 131. The width d3 of the triangular prism structure 141 is greater than the width d1 of the first rectangular structure 121.

Referring to FIG. 5, an embodiment of a method of making the pine shaped metal nano-scaled grating 10 comprises:

S10, providing a substrate 100;

S20, forming a first metal layer 120 on the substrate 100, forming an isolation layer 130 on the first metal layer 120, and locating a second metal layer 140 on the isolation layer 130;

S30, placing a first mask layer 151 on the second metal layer 140, wherein the first mask layer 151 covers partial surface of the second metal layer 140, and other surface is exposed;

S40, etching the second metal layer 140 to obtain a plurality of parallel and spaced triangular prism structures 141;

S50, etching the isolation layer 130 to obtain a plurality of parallel and spaced second rectangular structures 131;

S60, etching the first metal layer 120 to obtain a plurality of parallel and spaced first rectangular structures 121; and

S70, removing the first mask layer 151 to obtain the pine shaped metal nano-scaled grating 10.

In step S10, the substrate 100 can be an insulating substrate or a semiconductor substrate which includes a smooth surface. The material of the substrate 100 can be glass, quartz, gallium nitride, gallium arsenide, sapphire, alumina, magnesium oxide, silicon, silicon dioxide, or silicon nitride. The size, thickness and shape of the substrate 100 can be selected according to need. In one exemplary embodiment, the material of the substrate 100 is quartz. The substrate 100 can be cleaned by using a standard process. Furthermore, the substrate 100 can be treated with a hydrophilic treatment.

In step S20, the first metal layer 120 is deposited on the substrate 100, and the second metal layer 140 is deposited on the isolation layer 130. The method of depositing the first metal layer 120 and the second metal layer 140 can be electron beam evaporation method or ion sputtering method. The material of the first metal layer 120 and the second metal layer 140 can be metals with surface plasmon polaritons, such as gold, silver, copper, and aluminum. In one exemplary embodiment, the material of the first metal layer 120 and the second metal layer 140 is gold. The thickness of the first metal layer 120 is in a range of 20 nanometers to 500 nanometers. Furthermore, the thickness of the first metal layer 120 can be in a range of 50 nanometers to 200 nanometers. In one exemplary embodiment, the thickness of the first metal layer 120 is 100 nanometers. The thickness of the second metal layer 140 should be greater than nanometers so that the second metal layer 140 can be a free-standing structure after removing the first mask layer 151. The free-standing structure is that the second metal layer 140 can keep a certain shape without any supporter. The thickness of the second metal layer 140 can be in a range of 40 nanometers to 800 nanometers. Furthermore, the thickness of the second metal layer 140 can be in a range of 130 nanometers to 400 nanometers. In one exemplary embodiment, the thickness of the second metal layer 140 is 200 nanometers.

The isolation layer 130 is used to isolate the first metal layer 120 and the second metal layer 140, thus the first metal layer 120 is not destroyed when the second metal layer 140 is etched. When the material of the first metal layer 120 is different from the material of the second metal layer 140, the isolation layer 130 can be omitted. The material of the isolation layer 130 can be metal or metal oxide, such as chromium, tantalum, tantalum oxide, titanium dioxide, silicon, or silicon dioxide. The thickness of the isolation layer 130 can be in a range of 5 nanometers to 100 nanometers. Furthermore, the thickness of the isolation layer 130 can be in a range of 5 nanometers to 60 nanometers. When the material of the isolation layer 130 is metal, the material of the isolation layer 130 should be different from the material of the first metal layer 120 and the second metal layer 140. In one exemplary embodiment, the material of the isolation layer 130 is chromium, and the thickness of the isolation layer 130 is 10 nanometers.

In step S30, the first mask layer includes a body 154, and the body 154 defines a plurality of fourth openings parallel with and spaced from each other. The method for making the first mask layer 151 can be optical etching method, plasma etching method, electron beam etching method, focused ion beam etching method, hot embossing method, or nanoimprinting method. In one exemplary embodiment, the first mask layer 151 is formed on the second metal layer 140 by nanoimprinting method. Compared with other methods, the nanoimprinting method for making the first mask layer 151 has a plurality of advantages, such as high precision, high efficiency, low energy consumption, low temperature operation, and low cost.

Referring to FIG. 6, the nanoimprinting method for making the first mask layer 151 on the second metal layer 140 comprises:

S301, providing a first mask layer preform 150 and a second mask layer preform 160 in that order on the second metal layer 140;

S302, providing a template 170 with nanoscale patterned surface, bonding the nanoscale patterned surface of the template 170 to the second mask layer preform 160 at room temperature, then pressing the template 170 and the second mask layer preform 160;

S303, removing the template 170 to transfer the nanoscale patterns of the template 170 to the surface of the second mask layer preform 160, wherein a fifth recessed portion 162 and a fifth convex portion 164 are formed on the surface of the second mask layer preform 160;

S304, removing a part of the second mask layer preform 160 to form a second mask layer 161 which defines a fifth opening 163, wherein the part of the second mask layer preform 160 corresponds to the fifth recessed portion 162, and a part of the first mask layer preform 150 corresponding to the fifth opening 163 is exposed;

S305, removing the part of the first mask layer preform 150 that is exposed;

S306, removing the second mask layer 161 to obtain a first mask layer 151.

In step S301, the material of the first mask layer preform 150 can be homemade photoresist or commercial photoresist, such as polymethylmethacrylate (PMMA), silicon on glass (SOG), ZEP520, hydrogen silsesquioxane (HSQ), SAL601. In one exemplary embodiment, the material of the first mask layer preform 150 is ZEP520.

The photoresist can be provided by spin coating or droplet coating. The method for making the first mask layer preform 150 comprises following steps: firstly, spin coating photoresist on the second metal layer 140, wherein the rotation speed can be in a range of 500 rpm to 6000 rpm, and the time can be in a range of 0.5 minutes to 1.5 minutes; secondly, baking the photoresist at a temperature of 140 degrees to 180 degrees for 3 minutes to 5 minutes. The first mask layer preform 150 is formed on the surface of the second metal layer 140. The thickness of the first mask layer preform 150 can be in a range of 160 nanometers to 380 nanometers. In one exemplary embodiment, the thickness of the first mask layer preform 150 is 260 nanometers.

The second mask layer preform 160 can be imprinted at room temperature, also should have good structural stability and high resolution. For example, the impression resolution of the second mask layer preform 160 can be less than 10 nanometers. The material of the second mask layer preform 160 can be HSQ, SOG, or other silicone oligomers. The thickness of the second mask layer preform 160 can be in a range of 80 nanometers to 280 nanometers. Furthermore, the thickness of the second mask layer preform 160 can be in a range of 100 nanometers to 160 nanometers. In one exemplary embodiment, the thickness of the second mask layer preform 160 is 121 nanometers. Since the second mask layer preform 160 can be mechanically embossed easily, the accuracy of nanoscale patterns formed on the first mask layer preform 150 is high. Thus the accuracy of etching the second metal layer 140 is improved. In one exemplary embodiment, the material of the second mask layer preform 160 is HSQ. The state of HSQ is water-soluble vitreous with good mobility at room temperature, and become a cross-linked state after dehydration. The HSQ can flow spontaneously into channels of the template under pressure.

The method for making the second mask layer preform 160 comprises following steps: firstly, spin coating the resist HSQ on the first mask layer preform 150, wherein the rotation speed is in a range of 3000 rpm to 6500 rpm, and the spin-coating time is in a range of 0.6 minutes to 1.8 minutes, the spin coating of the HSQ is performed under high pressure; secondly, curing the resist HSQ to form a second mask layer preform 160.

In step S302, the template 170 can be a positive template or a negative template. In one exemplary embodiment, the template 170 is a negative template. The template 170 includes a plurality of spaced sixth recesses 172 and a plurality of sixth convex portions 174 between adjacent sixth recesses 172. The sixth recesses 172 can be stripe-shaped recesses or lattice-shaped recesses. In one exemplary embodiment, the sixth recesses 172 are stripe-shaped recesses, the sixth convex portions 174 are stripe-shaped convex portions, the sixth recesses 172 and the sixth convex portions 174 are arranged alternately. Furthermore, the sixth recesses 172 extend along the straight line to the edges of the template 170. Each sixth recess and sixth convex portion form an unit. The length of the unit can be in a range of 90 nanometers to 1000 nanometers. Furthermore, the length of the unit can be in a range of 121 nanometers to 650 nanometers. The width of the sixth recess 172 can be equal to the width of the sixth convex portions 174 or not. The width of the sixth recess 172 can be in a range of 40 nanometers to 450 nanometers. The width of the sixth convex portions 174 can be in a range of 50 nanometers to 450 nanometers. In one exemplary embodiment, the length of the unit is 200 nanometers, the width of the sixth recess 172 is 100 nanometers. The height of the sixth convex portions 174 can be in a range of 10 nanometers to 1000 nanometers. Furthermore, the height of the sixth convex portions 174 can be in a range of 20 nanometers to 800 nanometers. Furthermore, the height of the sixth convex portions 174 can be in a range of 30 nanometers to 700 nanometers. In one exemplary embodiment, the height of the sixth convex portions 174 is 200 nanometers.

The material of the template 170 can be hard materials such as nickel, silicon, or silicon dioxide. The material of the template 170 can also be flexible materials such as PET, PMMA, or PS. In one exemplary embodiment, the material of the template 170 is silicon dioxide.

The surface having nanoscale patterns of the template 170 is bonded to the second mask layer preform 160 at room temperature. When the template 170 is pressed, the degree of vacuum is in a range of 5×10⁻⁴-1.5×10⁻² bar and the applied pressure is in a range of 2 Psi to 100 Psi, and the time of applying pressure is in a range of 2 minutes to 30 minutes. In one exemplary embodiment, the degree of vacuum is 10⁻³ bar, the applied pressure is 25 Psi, the time of applying pressure is 5 minutes.

The sixth convex portions 174 of the template 170 are presses into the inside of the second mask layer preform 160 and the second mask layer preform 160 is deformed under the pressure to form a preform layer having nanoscale patterns. The part of the second mask layer preform 160 corresponding to the sixth convex portions 174 is compressed to form the fifth recesses 162. The HSQ flows into the sixth recess 172 of the template 170 under pressure, and the fifth convex portion 164 is formed on the second mask layer preform 160.

In step S303, a plurality of parallel and spaced fifth recesses 162 and fifth convex portions 164 are formed on the preform layer after removing the template 170. The size and shape of the fifth recesses 162 are the same as that of the sixth convex portions 174. The size and shape of the fifth convex portions 164 are the same as that of the sixth recesses 172. The depth of the fifth recesses 162 is in a range of 100 nanometers to 190 nanometers.

In step S304, the part of the second mask layer preform 160 corresponding to the fifth recesses 162 can be removed by plasma etching method. The etching gas can be selected according to the material of the second mask layer preform 160. In one exemplary embodiment, the part of the second mask layer preform 160 can be removed by fluorocarbon (CF₄) reactive plasma etching to form the second mask layer 161. The power of the CF₄ reactive plasma etching is in a range of 10 watts to 150 watts; the volumetric flow rate of the CF₄ plasma is in a range of 2 sccm to 100 sccm (standard-state cubic centimeter per minute); the pressure is in a range of 1 Pa to 15 Pa, the etching time is in a range of 2 seconds to 4 minutes. In one exemplary embodiment, the power of the etching system is 40 watts, the volumetric flow rate of the CF₄ plasma is 26 sccm, the pressure is 2 Pa, and the etching time is 10 seconds. The part of the second mask layer preform 160 corresponding to the fifth recesses 162 are removed by etching to form the fifth openings 163. The part of the second mask layer preform 160 corresponding to the fifth convex portions 164 is simultaneously etched and become thinner. The height of the fifth convex portions 164 is in a range of 90 nanometers to 180 nanometers.

In step S305, the part of the first mask layer preform 150 can be removed by oxygen gas plasma to form the first mask layer 151. The power of the oxygen gas plasma system is in a range of 10 watts to 250 watts, the volumetric flow rate of oxygen gas plasma is in a range of 2 sccm to 100 sccm, the air pressure is in a range of 0.5 Pa to 50 Pa, the etching time is in a range of 5 seconds to 5 minutes. In one exemplary embodiment, the power of the oxygen gas plasma system is 78 watts, the volumetric flow rate of oxygen gas plasma is 12 sccm, the air pressure is 26 Pa, the etching time is seconds. After the part of the first mask layer preform 150 being removed, the first mask layer preform 150 defines a fourth opening 153 corresponding to the fifth opening 163. The second metal layer 140 corresponding to the fourth opening 153 is exposed. Since the HSQ is crosslinked under oxygen gas plasma, the fifth convex portions 164 can allow the first mask layer 151 to have a high resolution.

In step S306, the second mask layer 161 can be removed by solvent. Since the second mask layer 161 can be dissolved and the first mask layer 151 can not be dissolved by the solvent, when the second mask layer 161 is removed, the first mask layer is exposed and not removed. In one exemplary embodiment, the solvent is water. After the second mask layer 161 being removed, the body 154 of the first mask layer 151 is exposed, and the body 154 corresponds to the fifth convex portions 164.

In step S40, the structure obtained after the step S30 is placed in a reactive plasma system for etching, thus a plurality of parallel and spaced triangular prism structures 141 are obtained, the plurality of triangular prism structures 141 are arranged. The etching gas in the etching system is a mixed gas of a physical etching gas and a reactive etching gas. The physical etching gas can be argon gas, or helium, and the reactive etching gas can be oxygen gas, chlorine, boron trichloride, or tetrachloride carbon. The physical etching gas and the reactive etching gas can be selected according to the material of the second metal layer 140 and the first mask layer 151 so that the etching gas has a higher etching rate. For example, when the material of the second metal layer 140 is gold, platinum, or palladium, the physical etching gas is argon gas. When the material of the second metal layer 140 is copper, the physical etching gas is helium. When the material of the second metal layer 140 is aluminum, the physical etching gas is argon gas. In one exemplary embodiment, the physical etching gas is argon gas, and the reactive etching gas is oxygen gas.

The physical etching gas and the reactive etching gas are introduced into the etching system. On the one hand, the body 154 of the first mask layer 151 is progressively etched by the reactive etching gas; on the other hand, the exposed second metal layer 140 can also be etched by the physical etching gas. As the first mask layer 151 is progressively etched, the width of the fourth opening 153 gradually becomes greater. Since the exposed part of the second metal layer 140 corresponds to the fourth opening 153, the etching width of the exposed part gradually becomes greater from bottom to top. The first mask layer 151 can be removed or partially removed by the reactive etching gas. The exposed part of the second metal layer 140 can be removed or partially removed by the physical etching gas. The ratio between the horizontal etching rate and the vertical etching rate can be selected by adjusting the relationship of volumetric flow, pressure and power of argon gas and oxygen gas. The triangular prism structures 141 can be obtained by adjusting the ratio. The second metal layer 140 defines a plurality of parallel and spaced third openings 143 and comprises a plurality of triangular prism structures 141. The isolation layer 130 is exposed through the third openings 143.

The volume flow rate of the physical etching gas is in a range of 20 sccm to 300 sccm. The volume flow rate of the reactive etching gas is in a range of 2 sccm to 20 sccm. The pressure of the etching system is in a range of 16 Pa to 180 Pa, the power of the etching system is in a range of 11 watts to 420 watts, and the etching time is in a range of 5 seconds to 3 minutes. In one exemplary embodiment, the volumetric flow rate of argon gas is 48 sccm, the volumetric flow rate of oxygen gas is 5 sccm, the pressure of the etching system is 26 Pa, the power of the etching system is 70 watts, and the etching time is in a range of 15 seconds to 20 seconds.

In step S50, a plurality of parallel and spaced second rectangular structures 131 can be obtained by etching the isolation layer 130. In one exemplary embodiment, the material of the isolation layer 130 is chromium, the etching gas is a mixed gas of oxygen gas and chlorine gas. The power of the reactive plasma system can be in a range of 5 watts to 210 watts. Furthermore, the power of the reactive plasma system can be in a range of 10 watts to 88 watts. In one exemplary embodiment, the power of the reactive plasma system is 22 watts. The volume flow rate of oxygen gas can be in a range of 3 sccm to 35 sccm, the volume flow rate of chlorine gas can be in a range of 6 sccm to 200 sccm. In one exemplary embodiment, the volume flow rate of oxygen gas is 5 sccm, and the volume flow rate of chlorine gas is 26 sccm, the air pressure is in a range of 8 Pa to 150 Pa, the pressure of the system is 26 Pa. The etching time is in a range of 5 seconds to 1 minutes. In one exemplary embodiment, the etching time is 15 seconds.

The isolation layer 130 defines a plurality of parallel and spaced second openings 133 and comprises a plurality of second rectangular structures 131. The second openings 133 is stripe shaped. The second openings 133 correspond to the third openings 143, and the second rectangular structures 131 correspond to the triangular prism structures 141. The first metal layer 120 is exposed through the second openings 133.

In step S60, the etching the first metal layer 120 is performed in a reactive plasma system.

The physical etching gas and the reactive etching gas are introduced into the etching system. The physical etching gas is argon gas, and the reactive etching gas is a mixture of chlorine gas and oxygen gas. The physical etching gas and the reactive etching gas simultaneously etch the first metal layer 120.

A plurality of first openings 123 are obtained by etching a part of the first metal layer 120 corresponding to the second openings 133. In addition, some metal particles or powders can be produced and fall off from the first metal layer 120 during the etching process. If there is no reactive etching gas, the metal particles or powders will accumulate along the sidewalls of the first openings 123 to form a thick edge, and that will also result in a large surface roughness of the sidewalls of the first openings 123. A gradient of the etching rate of the first metal layer 120 along each direction tends to be stable. Since the metal particles or powders are deposited on the bottom surfaces of the first openings 123, the accumulation of the metal particles or powders on the bottom surfaces of the first openings 123 is equal to a reduction in the vertical etching rate and also equal to an increase in the horizontal etching rate. The excess metal particles or powders deposited on the sidewalls of the first openings 123 can be etched by the reactive etching gas and the physical etching gas. The first rectangular structures 121 have a regular structure and a small surface roughness.

The volume flow rate of chlorine gas can be in a range of 1 sccm to 240 sccm. Furthermore, the volume flow rate of chlorine gas can be in a range of 1 sccm to 100 sccm. In one exemplary embodiment, the volume flow rate of chlorine gas is 5 sccm. The volume flow rate of oxygen gas can be in a range of 1 sccm to 260 sccm. Furthermore, the volume flow rate of oxygen gas can be in a range of 1 sccm to 100 sccm. In one exemplary embodiment, the volume flow rate of oxygen gas is 10 sccm. The volume flow rate of argon gas can be in a range of 50 sccm to 500 sccm. In one exemplary embodiment, the volume flow rate of argon gas is 78 sccm. The pressure of the system can be in a range of 8 Pa to 110 Pa. In one exemplary embodiment, the pressure of the system is 16 Pa. The power of the system can be in a range of 20 watts to 300 watts. In one exemplary embodiment, the power of the system is 121 watts. The etching time can be in a range of 5 minutes to 50 minutes. Furthermore, the etching time can be in a range of 8 minutes to 13 minutes. In one exemplary embodiment, the etching time is 11 minutes.

The shape of the first openings 123 is regular rectangle after the step S60 being completed. The width of the first openings 123 is in a range of 10 nanometers to 350 nanometers. The width of the first openings 123 can be controlled by adjusting the etching time. The thickness of the first rectangular structures 121 can be controlled by adjusting the etching time. In one exemplary embodiment, the width of the first openings 123 is 150 nanometers.

In step S70, the residual photoresist remains in the structure obtained by step S60. The pine shaped metal nano-scaled grating 10 is obtained by removing the residual photoresist. The residual photoresist can be resolved by dissolving agent. The dissolving agent can be tetrahydrofuran (THF), acetone, butanone, cyclohexane, n-hexane, methanol, absolute ethanol, or non-toxic or low toxicity of environmentally friendly solvents. In one exemplary embodiment, the residual photoresist is removed by ultrasonic cleaning in acetone solution. FIG. 7 and FIG. 8 are SEM images of the pine shaped metal nano-scaled grating.

Referring to FIG. 9, an embodiment of a method of making the pine shaped metal nano-scaled grating 20 comprises:

S10A, providing a substrate 200;

S20A, forming a first metal layer 220 on the substrate 200, forming an isolation layer 230 on the first metal layer 220, and locating a second metal layer 240 on the isolation layer 230;

S30A, placing a first mask layer 251 on the second metal layer 240, wherein the first mask layer 251 covers partial surface of the second metal layer 240, and other surface is exposed;

S40A, etching the second metal layer 240 to obtain a plurality of triangular prism structures 241;

S50A, etching the isolation layer 230 to obtain a plurality of second rectangular structures 231;

S60A, etching the first metal layer 220 to obtain a plurality of first rectangular structures 221; and

S70A, depositing a third metal layer 261 on the triangular prism structures 241 to obtain a three-dimensional nanostructures 210.

The method of making the pine shaped metal nano-scaled grating 20 is similar to the method of making the pine shaped metal nano-scaled grating 10 except that the third metal layer 261 is deposited on the triangular prism structures 241 without removing the first mask layer 251. The thickness of the third metal layer 261 is greater than 30 nanometers. In one exemplary embodiment, the thickness of the third metal layer 261 is 50 nanometers.

On the one hand, the method of depositing the third metal layer 261 on the triangular prism structures can adjust the charge distribution in the preparation process, which is beneficial to the processing. On the other hand, the mask layer don't need to be removed, so procedures of the method are simple. The pine shaped metal nano-scaled grating prepared by the above method can make the diffraction precision reach several hundred nanometers.

Referring to FIG. 10, an embodiment of a pine shaped metal nano-scaled grating 30 comprises a substrate 300 and a plurality of three-dimensional nanostructures 310. The substrate 300 defines a first surface 3002 and a second surface 3004 corresponding to the first surface 3002. The plurality of three-dimensional nanostructures 310 are located on both the first surface 3002 and the second surface 3004. The three-dimensional nanostructures 310 are pine shaped structures. The three-dimensional nanostructures 310 comprises a first rectangular structure 321, a second rectangular structure 331, and a triangular prism structure 341. The first rectangular structure 321 is located on the substrate 300. The second rectangular structure 331 is located on the first rectangular structure 321. The triangular prism structure 341 is located on the second rectangular structure 331. The width of the bottom surface of the triangular prism structure 341 is equal to the width of the top surface of the second rectangular structure 331 and larger than the width of the top surface of the first rectangular structure 321.

The structure of the pine shaped metal nano-scaled grating 30 is similar to the structure of the pine shaped metal nano-scaled grating 10 except that the plurality of pine shape nanostructures 310 are located on both the first surface 3002 and the second surface 3004.

Referring to FIG. 11, an embodiment of a pine shaped metal nano-scaled grating 40 comprises a substrate 400 and a plurality of three-dimensional nanostructures 410. The plurality of three-dimensional nanostructures 410 are located on at least one surface of the substrate 400. The three-dimensional nanostructures 410 is pine shape structures. The three-dimensional nanostructures 410 comprises a rectangular structure 421 and a triangular prism structure 441. The rectangular structure 421 is located on the substrate 400. The triangular prism structure 441 is located on the rectangular structure 421. The width of the bottom surface of the triangular prism structure 441 is greater than the width of the top surface of the rectangular structure 421.

Referring to FIG. 12, an embodiment of a method of making the pine shaped metal nano-scaled grating 40 comprises:

S10B, providing a substrate 400;

S20B, forming a first metal layer 420 on the substrate 400, and locating a second metal layer 440 on the first metal layer 420;

S30B, placing a first mask layer 451 on the second metal layer 440, wherein the first mask layer 251 covers partial surface of the second metal layer 440, and other surface is exposed;

S40B, etching the second metal layer 440 to obtain a plurality of parallel and spaced triangular prism structures 441;

S50B, etching the first metal layer 420 to obtain a plurality of parallel and spaced rectangular structures 421; and

S60B, removing the first mask layer 451 to obtain the pine shaped metal nano-scaled grating 40.

The structure of the pine shaped metal nano-scaled grating 40 is similar to the structure of the pine shaped metal nano-scaled grating 10 except that the pine shape structures consist of the rectangular structures 421 and the triangular prism structures 441. The material of the rectangular structures 421 and the triangular prism structures 441 is metal material. The material of the triangular prism structures 441 is different from the material of the rectangular structures 421.

The triangular prism structure of the pine shaped metal nano-scaled grating is equivalent to the T-gate. The preparation of T-gate by the above method is also within the scope of the disclosure.

The pine shaped metal nano-scaled grating of the disclosure has many applications. The pine shaped metal nano-scaled grating can realize resonance of light at different wavelengths, and the third openings between adjacent triangular prism structures can achieve narrowband resonance. The half width of the narrowband resonance is in a range of 0.1 nanometers to 3 nanometers. The wavelength of the formant is in a range from near ultraviolet band to mid-infrared band. The disclosure can realize the manual operation of light. The light intensity and light conduction at nanometer scale can be controlled by using the surface plasmon resonance of the pine metal nanometer grating. The first openings between the two adjacent first rectangular structures can achieve broadband absorption. The first openings can absorb energy and radiate energy in other forms. For example, the first openings can absorb solar energy, and the solar energy is converted into the energy required for chemical reactions, so the first openings can play a photocatalytic role. The pine shaped metal nano-scaled gratings have a good effect in validating the theoretical model of Fano resonance.

Compared to the prior art, the pine shaped metal nano-scaled grating of the disclosure has many advantages. Firstly, the pine shaped metal nano-scaled grating is composed of at least two parts, and different parts can achieve different effects. Each part constitutes a resonant cavity with a different width. Each resonant cavity can absorb photons near the corresponding resonant waves. The structure of the pine shaped metal nano-scaled grating can effectively extend the range of resonant waves. The triangular prism structures can achieve narrowband resonance absorption, and the rectangular structures can achieve broadband absorption. Secondly, the third metal layer is deposited on the surface of the hybrid structure of the photoresist and second metal layer, and the above structure can adjust the charge distribution of the metal layer. Thirdly, the pine shaped metal nano-scaled grating can be made by the reactive ion etching method. The method can achieve vertical and lateral anisotropic etching. The method can also achieve anisotropic etching in vertical direction to obtain the nanostructures. Fourthly, the nanostructure and the method of making the nanostructure have a wide application field. The pine shaped metal nano-scaled gratings have excellent optical properties in the near and far fields. The grating direction of the pine shaped metal nano-scaled grating can be changed.

The embodiments shown and described above are only examples. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, including in matters of shape, size, and arrangement of the parts within the principles of the present disclosure up to, and including, the full extent established by the broad general meaning of the terms used in the claims.

Depending on the embodiment, certain of the steps of methods described may be removed, others may be added, and the sequence of steps may be altered. The description and the claims drawn to a method may comprise some indication in reference to certain steps. However, the indication used is only to be viewed for identification purposes and not as a suggestion as to an order for the steps. 

What is claimed is:
 1. A method of making a pine shaped metal nano-scaled grating, the method comprising: forming a first metal layer on a substrate, forming an isolation layer on the first metal layer, and locating a second metal layer on the isolation layer; placing a first mask layer on the second metal layer, wherein the first mask layer comprises a body, and the body defines a plurality of openings parallel with and spaced apart from each other; etching the first mask layer and the second metal layer to obtain a plurality of triangular prism structures; etching the isolation layer to obtain a plurality of second rectangular structures using the plurality of triangular prism structures as a first mask; and etching the first metal layer to obtain a plurality of first rectangular structures using the plurality of second rectangular structures as a second mask.
 2. The method as claimed in claim 1, wherein a first thickness of the first metal layer is in a range of 20 nanometers to 500 nanometers, a second thickness of the isolation layer is in a range of 5 nanometers to 100 nanometers, and a third thickness of the second metal layer is in a range of 40 nanometers to 800 nanometers.
 3. The method as claimed in claim 1, wherein the first metal layer comprises a first material selected from the group consisting of gold, silver, copper, and aluminum; the second metal layer comprises a second material selected from the group consisting of gold, silver, copper, and aluminum.
 4. The method as claimed in claim 1, wherein the isolation layer comprises a third material selected from the group consisting of chromium, thallium, thallium oxide, titanium dioxide, silicon, and silica.
 5. The method as claimed in claim 1, wherein the first mask layer and the second metal layer is etched by a mixed gas of a physical etching gas and a reactive etching gas in an etching system, a first volume flow rate of the physical etching gas is in a range of 20 sccm to 300 sccm, a second volume flow rate of the reactive etching gas is in a range of 2 sccm to 20 sccm, a pressure of the etching system is in a range of 16 Pa to 180 Pa, a power of the etching system is in a range of 11 watts to 420 watts, and an etching time is in a range of 5 seconds to 3 minutes.
 6. The method as claimed in claim 1, wherein the isolation layer is etched by a mixed gas of oxygen gas and chlorine gas in an etching system, a first volume flow rate of the oxygen gas is in a range of 3 sccm to 35 sccm, a second volume flow rate of the chlorine gas is in a range of 6 sccm to 200 sccm, a pressure of the etching system is in a range of 8 Pa to 150 Pa, a power of the etching system is in a range of 5 watts to 210 watts, an etching time is in a range of 5 seconds to 1 minutes.
 7. The method as claimed in claim 1, wherein the first metal layer is etched by a mixed gas of oxygen gas, argon gas and chlorine gas in an etching system, a first volume flow rate of the chlorine gas is in a range of 1 sccm to 240 sccm, a second volume flow rate of the oxygen gas is in a range of 1 sccm to 260 sccm, a third volume flow rate of the argon gas is in a range of 50 sccm to 500 sccm, a pressure of the etching system is in 16 Pa, a power of the etching system is in a range of 20 watts to 300 watts, an etching time is in a range of 5 minutes to 50 minutes.
 8. The method as claimed in claim 1, wherein the plurality of openings are arranged side by side and extends along a straight line, a fold line, or a curve line, the width of the plurality of openings is in a range of 40 nanometers to 450 nanometers.
 9. The method as claimed in claim 1, wherein a bottom surface of the triangular prism structure is completely coincident with an top surface of the second rectangular structure.
 10. The method as claimed in claim 1, further comprising depositing a third metal layer on the plurality of the triangular prism structures after obtaining the plurality of first rectangular structures.
 11. A method of making a pine shaped metal nano-scaled grating, the method comprising: forming a first metal layer on a substrate, forming a second metal layer on the first metal layer, wherein the first metal layer comprises a first metal and the second metal layer comprises a second metal, the first metal is different from the second metal; placing a first mask layer on the second metal layer, wherein the first mask layer comprises a body, and the body defines a plurality of openings parallel with and spaced apart from each other; etching the first mask layer and the second metal layer to obtain a plurality of triangular prism structures; and etching the first metal layer to obtain a plurality of rectangular structures.
 12. The method as claimed in claim 11, wherein the first metal layer comprises a material selected from the group consisting of gold, silver, copper, and aluminum; the second metal layer comprises a material selected from the group consisting of gold, silver, copper, and aluminum. 